1. Field of the Invention
The present invention relates to a keypad assembly for a cellular phone, and more particularly to a light emitting keypad assembly that is able to emit a great deal of light.
2. Description of Related Art
Cellular phones often are people's most popular electronic appliances and make people available virtually everywhere. A conventional cellular phone only has a basic communication function. However, people want to have more functions on their cellular phones. A keypad assembly on a cellular phone can emit light selectively when requested by a user.
With reference to FIG. 3, a conventional keypad assembly for a cellular phone is mounted on a substrate (30) of a cellular phone and comprises a silicon layer (33), multiple protrusions (34), multiple light-emitting diodes (LEDs)(32), multiple keys (35) and a protective layer (36). The silicon layer (33) has top and bottom. The protrusions (34) are formed on the bottom of the silicon layer (33) and correspond to and engage an electrical tab (31) of the substrate (30). The LEDs (32) are mounted on the bottom of the silicon layer (33) between the protrusions (34) and the contacts (31). The keys (35) are formed on the top of the silicon layer (33) and cause the LEDs (32) to emit light when the keys (35) are pressed. Light from the LEDs (32) passes through the silicon layer (33) and indirectly lights the keys (35) since the light cannot directly pass through the keys (35). The protective layer (36) is formed on the top of the silicon layer (33) between the keys (35).
As cellular phones continue to get smaller and smaller, large and bright LEDs (32) are not able to fit into the cellular phone.
The manufacturers of keypads for cellular phones have begun to use a luminescent layer as a light source to replace the LEDs (32) and accommodate the smaller size of the new cellular phones. With reference to FIG. 4, a luminescent layer (40) is mounted between the silicon layer (33) and the substrate (30). When the keys (35) are pressed down, the protrusions (34) press the luminescent layer (40) and the contacts (31). The luminescent layer (40) emits light, and the light of the luminescent layer (40) passes through the silicon layer (33) and is emitted from the top of the silicon layer (33). Because the luminescent layer (40) is between the silicon layer (33) and the substrate (30), the protrusions (34) have difficulty pressing the contacts (31) when the protrusions (34) are pressed. Furthermore, a conventional light-emitting layer a luminescent layer (40) is at the bottom of the luminescent layer (40) so the brightness of light emitted from the luminescent layer (40) is greatly reduced.
To overcome the shortcomings, the present invention provides a light emitting keypad assembly to obviate or mitigate the aforementioned problems.